Investments, Debt and Equity Securities (Limited Partnerships and Real Estate Joint Ventures) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	$ 2,327	$ 1,996
Equity Method Investments
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	934	780
Limited partnership Fair Value Member
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	683	581
Cost-method Investments
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	49	63
Corporate Joint Venture
Real Estate [Line Items]
Real Estate Investments, Joint Ventures	$ 661	$ 572